The present invention relates to a power-generation detection circuit and, in particular, to power-generation detection for use in an electronic device which is driven by an AC power generated by motion of a rotating weight or motion of a spring. The invention further relates to a semiconductor device in which the power-generation detection circuit is formed. And more in particular an electronic device, having the power-generation detection circuit, which is a timepiece and a power-generation detection method and a power consumption control method for operating the electronic device.
In a compact portable electronic device, such as a wrist watch, it is known to incorporate a power-generation device therein to obtain power for driving the electronic device without a battery. Referring now to FIG. 15, there is shown a simplified configuration of an electronic device which incorporates a power-generation device 6. This portable electronic device includes an electromagnetic power-generation device as the power-generation device 6. Power-generation device 6 includes a rotating weight 7 that moves in a swinging motion when the electronic device is moved or shaken, a train wheel mechanism 8 for transmitting the rotating motion of rotating weight 7, a stator 9 and a rotor 10. When rotor 10 rotates, an electromotive force is generated by an output coil 11 of stator 9, so that an AC power is output In addition, the AC power output from electromagnetic generator 6 is full-wave rectified by a rectification diode bridge 12 to supply the power to a large-capacity capacitor 13 and a circuit unit 14 of the electronic device. When no power generation is performed by electromagnetic generator 6, circuit unit 14 is driven by power stored in large-capacity capacitor 13. For this reason, the portable electronic device can continuously operate circuit unit 14 without a battery.
Because the electronic device described above has no means for detecting the state of power generation supplied from power-generation device 6, the current consumption of circuit unit 14 is constant regardless of the state of power generation of power-generation device 6. As a result, power is consumed by circuit unit 14 even while no power is being generated by power-generation device 6. This may result in large-capacity capacitor 13 being discharged within a short period of time with the possibility of circuit unit 14 stopping completely.
The present invention is for a power-generation detection circuit for detecting the state of power generation in an electronic device. In accordance with the present invention, a power-generation detection circuit is provided which includes a switching element for performing a switching operation in response to the cycle of an externally generated AC power signal. A capacitor element is coupled to the switch for storing charges depending on the state of the switch, the capacitor element having a discharge path. A discharging element is inserted in the discharging path of the capacitor element for discharging the charges stored in the capacitor element. A voltage detector is coupled to the capacitor element for detecting whether voltage of the capacitor element exceeds a predetermined value.
In an exemplary embodiment, the discharging element of the power-generation detection circuit of the present invention is a resistor element.
In an exemplary embodiment, the discharging element of the power-generation detection circuit of the present invention is a constant-current circuit. The constant-current circuit of the power-generation detection circuit of the present invention includes a constant-current source and a current mirror circuit.
In an exemplary embodiment, the power-generation detection circuit of the present invention includes a current-limiter connected in series with the capacitor element for limiting the charge current of the capacitor element.
In an exemplary embodiment, the voltage detector of the power-generation detection circuit of the present invention is an inverter circuit.
In an exemplary embodiment, the voltage detector of the power-generation detection circuit of the present invention is a Schmidt trigger inverter circuit.
In an exemplary embodiment, the voltage detector of the power-generation detection circuit of the present invention is a comparator circuit.
In an exemplary embodiment, the switching element of the power-generation detection circuit of the present invention is a transistor. The transistor may be a MOS transistor or a bipolar transistor.
In accordance with the present invention, a semiconductor device is provided which includes a switching element for performing a switching operation in response to the cycle of an externally generated AC power signal. A capacitor element is coupled to the switch for storing charges depending on the state of the switch, the capacitor element having a discharge path. A discharging element is inserted in the discharging path of the capacitor element for discharging the charges stored in the capacitor element. A voltage detector is coupled to the capacitor element for detecting whether a voltage of the capacitor element exceeds a predetermined value.
In an exemplary embodiment, the discharging element of the semiconductor device of the present invention is a constant-current source and a current mirror circuit. The current mirror circuit of the semiconductor device of the present invention is a pair of transistors.
In an exemplary embodiment, the switching element of the semiconductor device of the present invention is a transistor. The transistor may be a MOS transistor or a bipolar transistor.
In accordance with the present invention, an electronic device is provided which includes a power-generation device for generating AC power. A power-generation detection circuit, coupled to the power generation device, includes a switching element for performing a switching operation in response to the cycle of AC power generated by the power-generation device; a capacitor element is coupled to the switch for storing charges depending on the switching operation performed by the switching element, the capacitor element having a discharge path; a discharging element is inserted in the discharging path of the capacitor element for discharging the charges stored in the capacitor element, and a voltage detector is coupled to the capacitor element for detecting whether a voltage of the capacitor element exceeds a predetermined value.
In an exemplary embodiment, the power-generation device of the electronic device has a rotating weight for performing swinging motion and a power-generation element for generating electromotive force from the rotating motion of the rotating weight.
In an exemplary embodiment, the power-generation device includes an elastic member on which deformation forces act. A rotating member rotates as a result of a recovery force generated by the elastic member returning to its original shape. A power-generation element generates electromotive force from the rotating motion of the rotating member.
In an exemplary embodiment, the power-generation includes a piezoelectric element which generates electromotive force by a piezoelectric effect when displacement acts on the piezoelectric element.
In accordance with the present invention, an electronic device is provided which includes a power-generation device for generating AC power. A power-generation detection circuit, coupled to the power generation device, includes a switching element for performing a switching operation in response to the cycle of the AC power generated by the power-generation device; a capacitor element, coupled to the switch, stores charges in response to the switching operation performed by the switching element. A discharging element, inserted in the discharging path of the capacitor element, discharges the charges stored in the capacitor element; a voltage detector, coupled to the capacitor element, detects whether a voltage across the capacitor element exceeds a predetermined value; and a control circuit is coupled to the voltage detector for controlling power consumption of the device in response to the detection of the voltage detector.
In an exemplary embodiment, the control circuit of the electronic device of the present invention determines that the power-generation device is not performing power generation when a voltage across the capacitor element is not more than the predetermined value, and, as a result, reduces power consumption of the device. The control circuit of the electronic device of the present invention determines that the power-generation device is performing power generation when a voltage across the capacitor element exceeds the predetermined value, and, as a result, cancels the reduction in power consumption.
In an exemplary embodiment, the control circuit of the electronic device of the present invention controls the power consumption of the device based on the length of time in which a voltage across the capacitor element exceeds the predetermined value.
In accordance with the present invention, a timepiece includes a power-generation device for generating AC power. A power-generation detection circuit, coupled to the power-generation device includes a switching element, coupled to the power-generation device, for performing a switching operation in response to a cycle of AC power generated by the power-generation device; a capacitor element, coupled to the switching element, stores charges in response to the switching operation performed by the switching element; a discharging element is inserted in a discharging path of the capacitor element for discharging the charges stored in the capacitor element; and a voltage detector is coupled to the discharge element for detecting that a voltage across the capacitor element exceeds a predetermined value; and a timer circuit for counting time.
In an exemplary embodiment of the timepiece of the present invention, the power-generation detection device, power-generation circuit, and timer circuit are included in a housing of a wrist watch.
In an exemplary embodiment of the timepiece of the present invention, the power-generation device, power-generation detection circuit, and timer circuit are included in a housing of a pocket watch.
In an exemplary embodiment of the timepiece of the present invention, the power-generation device, power-generation detection circuit, and timer circuit are included in a housing of a table timepiece.
In accordance with the present invention, a power-generation detection method is provided that includes the steps of charging a capacitor element by a switching operation in response to a cycle of AC power which is externally generated; discharging the capacitor element when charging of the capacitor element is not performed; determining whether the voltage across the capacitor element is a predetermined voltage; and determining that power generation is being performed when the voltage across the capacitor element exceeds the predetermined voltage.
In accordance with the present invention, a power consumption control method is provided that includes the steps of charging a capacitor element by a switching operation in response to a cycle of AC power 8 which is externally generated; discharging the capacitor element when charging of the capacitor element is not performed, determining whether the voltage of the capacitor element is a predetermined voltage; determining that no power generation is performed when the voltage across the capacitor element does not exceed the predetermined voltage; and reducing power consumption of a circuit unit when no power generation is performed.
In an exemplary embodiment, a power consumption control method of the present invention also includes the steps of determining whether the voltage exceeds the predetermined voltage for a predetermined period of time, and canceling a reduction in power consumption of the circuit unit when the voltage exceeds the predetermined voltage for the predetermined period of time.
Accordingly, it is an object of the present invention to provide a power-generation detection circuit which can detect the state of generation power (i.e., the presence/absence of power generation and the strength of power generation) supplied from a power-generation device of an electronic device by a simple method so that power consumption of a circuit unit can be controlled depending on the detected state of power generation.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims.